Handle With Linux

Today I installed Eclipse IDE and the EPIC perl plugin. If you are learning a new programming language like me, you really need some kind of editor which has at least code coloring features. I remember once when I typed a piece of code from a book and I just couldn't get it to compile. I never finished this book because I spend a lot of time trying to find my mistake and I gave up on it in the end. A few years later I picked the book up again, but this time I had a little more experience and I typed the piece of code in a programming editor. This time I found the mistake almost immediately. There was a : where a ; should be.

IDE

Reading this text you really need to watch closely to see the difference between ;and: or ,and. when it is in code which is also new to you it's almost impossible to find. This was something I overlooked many times and in the editor it showed up immediately, because it had a different color and the line containing the error was marked.
To save myself some of these frustrating experiences I'm going to use an IDE this time.

Eclipse

My choice has fallen on the Eclipse IDE, I know there are many good perl editors out there and I don't have any knowledge about which is the best choice for what job. I do know the choice of editor is very personal and there are even people who use vi as a Perl IDE. My main reason for using Eclipse is because I've read about it on a forum and many people seemed to like it (and it's free). It seems to be a bit of overkill to write my very simple pieces of code in a full fledged IDE and I know it has some downsides too. Then again, I know sometimes code keeps on growing and IDE's often have a lot of benefits for big projects. I could write Perl code and execute it immediately on the command line. That would be an easy start, but I think it might be a good investment in the future to get used to an IDE, as I start my journey.

Installing Eclipse

Installing Eclipse is not too difficult, in Ubuntu I just selected it in the package manager and that was it.

Alternatively from the command line :

sudo apt-get install eclipse

I just went with all the defaults, to keep it simple.

Installing Epic plugin

Next step is installing Epic. Epic is a plugin for Eclipse which enables Perl development. To install the plugin start the IDE and select the workbench.

go to help menu

select software updates

select Find and install

Select search for new features to install

select New remote site

fill in any name you like (I named it Epic)

and the url:

http://e-p-i-c.sf.net/updates/testing

which I've got from the epic site. This is for the testing release, if you want to go for stable use this:

http://e-p-i-c.sf.net/updates/

next select the update site you just named and select finish.

Eclipse will start checking for updates immediately after the window closes.

After a while a new window pops up saying new updates are available, just check the plugin in this new window. And select next. That's it, now you can start perl projects in the IDE.

First Project

The downside to using a full IDE like this is that it's intended use is for big projects and that's why small programs still need a lot of extra stuff to work. You need to create a project first,

I did that by going to file > new > project and in the pop up wizard I selected perl > perl project

I named the project perltest (original eh?), and used the default location which is the directory workspace in my home directory.

After selecting finish I've got a project

First program

Now we need to create a file, so we go to file > new > file
Select the project (if it isn't selected yet)
I named the file perltest.pl

Selecting finish creates a new empty file in the workspace.

I want to see something quick so I just copy past some code into the workspace.

I found some interesting tutorials on the gtk2 site

So I took some source code from the tutorial:

http://gtk2-perl.sourceforge.net/doc/intro/code/widget_layout.pl

This is an interesting example, it shows me some of the things I can do with a few lines of code and what is more important, I can understand most of what it does and try messing around with it a bit.
If you want the full dissection of what it does I suggest you read the tutorial.

http://gtk2-perl.sourceforge.net/doc/intro/

Run configuration

After I pasted it in the editor I wanted to run it.
Here comes another downside of using an IDE, as I select run > run from the menu I'm asked for a configuration. From the command line I could run this program by just entering perl followed by the program name.
Thankfully it's all pretty straightforward I just select Perl Local and name a new configuration, select my project perltest and from there the file to run perltest.pl.
The run configuration is kept so I don't need to do this for this project again.

Messing with the code

Now comes the fun part:

Clicking run makes a window pop up with 2 buttons, I think that's pretty impressive as it doesn't complain about having library this or that installed or anything. (I run gnome, I guess the gtk libraries come with that)

So now I can start playing with it. As I didn't start by reading the tutorials I don't know what most of it does, but I can make out some things by using common sense.

I start first by trying to change some of the words to see if that's allowed:


my $quit_button = Gtk2::Button->new('_Start');

When I run it now it says start on the quit button, so that works.

I wonder what that underline does, as I see an underline on the S of the button I wonder if it has something to do with that. And indeed moving it to another place in the word makes another letter become underlined. This means I can change the activation key for this button by simply moving the underline in the word. This is very intuitive.

I'm very pleased to see I can change things in this code without even reading anything about it. I know this is no rocket science, but still I can imagine this stuff quickly becoming a lot of fun to learn.

The other button is a counter button which responds to clicking on it by adding up a counter in the window.

So It's pretty obvious what this piece of code does:

$inc_button->signal_connect( clicked => sub {
$label->set_text("Clicked $count times.");
$count++;
});

This must be a subroutine (it's named sub and I recognize the ++ as an increment funtction)
Let's add something to this thing.

$inc_button->signal_connect( clicked => sub {
$label->set_text("Clicked $count times.");
$count++;
$frame->set_border_width($count);
});

I took some of the code earlier in the script and modified it a bit, as I typed the $ a screen popped-up showing me the possible variables for code completion. This is one of the great helpful features of the IDE. Well in this case it doesn't do too much for me, but I now in serious stuff it's very nice to have.

I hoped this would make my window grow as I click the button... and it does.

This is fun.

What to do next?

The next step I guess would be trying to add another button, to make the thing shrink again.
I'm finished for today. I think I'm going to read into these tutorials a bit, because I really like the ease and intuitive rules of this language. I think this is going to give me lots of joy.

API docs

The only thing I'm really looking for is some kind of API documentation which describes the functions I can call so I can for instance use a button to make the background change color or something.

Suggestions?

If you think there are more fun ways of messing with this code, please let me now. If there's anything more that could help me learn this quicker I really appreciate helpful comments.
Some people commented on my previous article pointing me to other GUI toolkits for perl and even some RAD (Rapid Application Development) tools of which I didn't know they existed for perl.

I'll definitely take a look into that stuff and I'll write on my experiences in future articles.
It can take a while before comments get published as most readers are in a different time zone.

This is the second article in a ongoing series about learning perl GUI programming. You may be interested in the other articles too. You can find the other articles here:
1. starting perl GUI programming
2. Installing Eclipse, the Epic Perl plugin and my first Perl GUI program
3. Open Source rocks! Learning from code by debugging
4. Quick and dirty linux GUI programming
5. resources for learning Perl Graphical Programming
6. Drawing and animating directly to the Desktop with Perl
7. Dynamically-creating-gui-objects-on-demand-in-Perl